http_signatures.ex (2993B)
1 # Pleroma: A lightweight social networking server
2 # Copyright © 2017-2019 Pleroma Authors <https://pleroma.social/>
3 # SPDX-License-Identifier: AGPL-3.0-only
4
5 # https://tools.ietf.org/html/draft-cavage-http-signatures-08
6 defmodule Pleroma.Web.HTTPSignatures do
7 alias Pleroma.User
8 alias Pleroma.Web.ActivityPub.ActivityPub
9 alias Pleroma.Web.ActivityPub.Utils
10
11 require Logger
12
13 def split_signature(sig) do
14 default = %{"headers" => "date"}
15
16 sig =
17 sig
18 |> String.trim()
19 |> String.split(",")
20 |> Enum.reduce(default, fn part, acc ->
21 [key | rest] = String.split(part, "=")
22 value = Enum.join(rest, "=")
23 Map.put(acc, key, String.trim(value, "\""))
24 end)
25
26 Map.put(sig, "headers", String.split(sig["headers"], ~r/\s/))
27 end
28
29 def validate(headers, signature, public_key) do
30 sigstring = build_signing_string(headers, signature["headers"])
31 Logger.debug("Signature: #{signature["signature"]}")
32 Logger.debug("Sigstring: #{sigstring}")
33 {:ok, sig} = Base.decode64(signature["signature"])
34 :public_key.verify(sigstring, :sha256, sig, public_key)
35 end
36
37 def validate_conn(conn) do
38 # TODO: How to get the right key and see if it is actually valid for that request.
39 # For now, fetch the key for the actor.
40 with actor_id <- Utils.get_ap_id(conn.params["actor"]),
41 {:ok, public_key} <- User.get_public_key_for_ap_id(actor_id) do
42 if validate_conn(conn, public_key) do
43 true
44 else
45 Logger.debug("Could not validate, re-fetching user and trying one more time")
46 # Fetch user anew and try one more time
47 with actor_id <- Utils.get_ap_id(conn.params["actor"]),
48 {:ok, _user} <- ActivityPub.make_user_from_ap_id(actor_id),
49 {:ok, public_key} <- User.get_public_key_for_ap_id(actor_id) do
50 validate_conn(conn, public_key)
51 end
52 end
53 else
54 _e ->
55 Logger.debug("Could not public key!")
56 false
57 end
58 end
59
60 def validate_conn(conn, public_key) do
61 headers = Enum.into(conn.req_headers, %{})
62 signature = split_signature(headers["signature"])
63 validate(headers, signature, public_key)
64 end
65
66 def build_signing_string(headers, used_headers) do
67 used_headers
68 |> Enum.map(fn header -> "#{header}: #{headers[header]}" end)
69 |> Enum.join("\n")
70 end
71
72 def sign(user, headers) do
73 with {:ok, %{info: %{keys: keys}}} <- Pleroma.Web.WebFinger.ensure_keys_present(user),
74 {:ok, private_key, _} = Pleroma.Web.Salmon.keys_from_pem(keys) do
75 sigstring = build_signing_string(headers, Map.keys(headers))
76
77 signature =
78 :public_key.sign(sigstring, :sha256, private_key)
79 |> Base.encode64()
80
81 [
82 keyId: user.ap_id <> "#main-key",
83 algorithm: "rsa-sha256",
84 headers: Map.keys(headers) |> Enum.join(" "),
85 signature: signature
86 ]
87 |> Enum.map(fn {k, v} -> "#{k}=\"#{v}\"" end)
88 |> Enum.join(",")
89 end
90 end
91 end